Well funny thing is, Pharos is actually hard the more equipment you have on your ... DPS ! Or that is my feeling.

First boss: dog calls seems to be related to %life HP of the boss, so the faster you kill him => the more dogs you have to manage at the same time
Zu: kill one egg, let one pop, kill the add, u good to go, he won't insta kill anything. Also feels like egg call is somewhat DPS related since I had parties with one DPS being on standby and just killing the adds and not dpsing boss.
Third boss: that's a boss ?
Siren: Stick to her except when she ports to border and your good to go. DPS seems also to play a huge part here as with really heavy dps, as a scholar or white mage I can't keep up with the healing debuff + charm + healing tank + dispelling bleed on tank. If you slow the dps, weirdly it goes through with a breeze

In the end when I do that dungeon I switch to spiritbounding equipment ^^ it goes better